1. Field of the Invention
The present invention relates to a device that controls opening and closing of a sliding door of a vehicle.
2. Description of the Related Art
A door opening/closing device is used to drive a sliding door of a vehicle. Moreover, a door opening/closing control device is used to control the sliding door in cooperation with the door opening/closing device.
The door opening/closing device includes a motor, a clutch, and a wire drum. The torque of the motor is transmitted to the wire drum via the clutch. Therefore, when the clutch is brought into a coupled state, motor torque is conveyed to the wire drum. When the clutch is brought into an uncoupled state, motor torque it not conveyed to the wire drum. The wire drum rotates to wind a wire cable from one side thereof and pulls out the wire cable from the other side to open and close the sliding door. A moving direction of the sliding door depends on a rotating direction of the wire drum.
The door opening/closing device includes a tension mechanism that applies tension to the wire cable. Moreover, clearance is provided in the clutch. The tension mechanism and the clearance in the clutch prevent the wire cable from slackening. On the other hand, when the vehicle is parked in a tilted state, particularly, when the front part of the vehicle is lower than the back part, the tension mechanism and the clearance in the clutch function as play so that the sliding door moves and pulsates, irrespective of the control the door opening/closing device, because of the dead weight of the sliding door. This phenomenon is hereafter referred to as hunting. There is a need for a door opening/closing control device that prevents such hunting.
Some door opening/closing control devices monitor current supplied to the motor, which is performing pulse width modulation (PWM) driving, and, when the current exceeds a predetermined value, judge that a foreign matter has been pinched in the sliding door and reverses the sliding door.
Japanese Patent Application Laid-Open No. H11-236783, for example, discloses an opening/closing control device that calculates a tilt angle of the vehicle and performs opening/closing control of the sliding door based on the tilt angle. The tilt angle is calculated based on a duty ratio of a motor, which is performing PWM driving. However, this opening/closing control device does not address the problem of hunting of the sliding door.
Moreover, the opening/closing control device disclosed in Japanese Patent Application Laid-Open No. H12-236783 erroneously judges that a foreign matter is pinched in the sliding door when the sliding door is not moving, even when there is no foreign matter pinched. Accordingly, the conventional opening/closing control device cannot sensitively judge whether a foreign matter is pinched.
Furthermore, there is a need to control the sliding door to open/close smoothly and gently when the vehicle is parked in a tilted state.